1. Technical Background
The present invention relates generally to systems and methods for analyzing patient samples.
2. Discussion
Spectrophotometric analysis is often applied to liquid samples to determine their contents. In general, the term “spectrophotometric” refers to capturing spectral response over a range of wavelengths and correlating a response for each of the wavelengths. A device that performs this analysis is referred to as a “spectrophotorheter.” Such spectrophotometric analysis has been performed with near-infrared and adjacent visible radiation, which is capable of ascertaining hemoglobin, glucose, albumin, lipoproteins, and many other sera components.
One challenge in performing spectrophotometric analysis has been that the samples are initially obtained in a variety of primary patient collection containers. These containers are usually tubes of varying diameters and lengths. In the case of a patient blood sample, the liquid is often centrifuged to separate the liquid serum or plasma from the cellular phases. Such tubes may have a patient identification label, varying and unpredictable amounts of the sera to be analyzed in the total sample, and contain a relatively large amount of sample liquid.
Prior spectrophotometric analysis systems are adequate to meet their design criteria, and they generally aliquot a portion of the sample into a secondary container or tube of a consistent size. This technique may add complexity and increase the time required for processing in a single sample. This measure may introduce additional equipment expenses and processing delays, and may involve spectrophotometric scanning through the patient label.
Examples of successful analyzers having a spectrophotometric measurement through the metering tip are shown in (i) U.S. Pat. No. 5,846,492, entitled “Sample Quality Measurement And/Or Analyte Measurement In Dispensing Tip Of An Analyzer,” issued to Jacobs et al. on Dec. 8, 1998; and also (ii) U.S. Pat. No. 6,013,528, entitled “Analyzer Throughput Featuring Through-The-Tip Analysis,” issued to Jacobs et al. on Jan. 11, 2000, which are both incorporated by reference.
Many clinical analyzers provide a generally serial or linear path of dependent events for processing each sample. This serial procedure is generally required to be performed in a specific order, and each step must be finished before the next can begin. For example, an analyzer process might include the steps of sample handling, aspirating a portion of the sample into a metering tip, dispensing a portion of the sample onto a test element or slide, and then disposing of the tip. The time required to completely process a single sample may be referred to as the processing time, and each step of the total time can be referred to as a timing cycle or the “heartbeat.”
Such an analyzer might include various components, including a sample handling bin or repository for holding primary collection containers, a metering probe or proboscis which can move around the stations of the analyzer, one or more preferably disposable tips attached to the proboscis, and a metering pump connected to the proboscis for creating partial vacuum or partial pressure to selectively suck up into the tip or dispense a specific amount of sample liquid. In addition, analyzers often include the components required for a thin film or wet chemistry system, such as a test element supply, an incubator, reagent and assay supply, etc.
It is desirable in general to minimize the amount of the sample required for use in an analyzer, because any portion of the sample that is used for a particular operation cannot be later used for another process or operation. When the analyzer is in use, the component that actually touches the liquid of the sample is the tip.
Many of the metering tips used in analyzers are disposable, though the tip may also be permanent. Disposable tips generally have a relatively narrow cylindrical end, connected to a small cone, which is in turn connected to a larger generally cylindrical body. For optimum accuracy of the reading, and to minimize the amount of sample necessary, it is desirable to do the spectrophotometric measurement through the intermediate cone of the metering tip.
As an example, the present invention will be described in relation to clinical analyzers and sample quality measurement. However, it should be understood that the present invention relates to any apparatus or method having the features of the present invention, and is not limited to a particular type of design.
One method of incorporating a sample quality capability into an analyzer might be to insert a sample quality measurement step in between the step of aspirating the sample into the tip, and the step of dispensing the sample onto the test element. However, the sample quality measurement might take as long as the amount of time to meter the sample onto the test element. This particular method would therefore undesirably increase the length of the timing cycle of the analyzer. In addition, this particular method would undesirably require initially aspirating a larger portion of the sample, to raise the liquid level into the intermediate cone of the metering tip. Moreover, this technique may require substantial enabling software to move the metering tip to a new location for the sample integrity reading.
Accordingly, the present invention preferably provides systems and methods for analyzing and/or detecting the sample and/or analytes, while the sample is in the metering tip used to aspirate the sample liquid and also dispense it onto a slide test element. In other words, the spectrophotometric analysis may be done on the sample liquid while it is still in the tip which may be converted into cuvette, without requiring an additional container or cuvette, and may include a measurement of sample quality.
A possible aspect of the present invention relates to enhancing throughput of an analyzer by conducting a sample quality measurement in a process that is parallel to the main analyzer timing cycle. The sample quality measurement may thus be arranged after a portion of the sample has already been dispensed onto the test element, and after the metering tip has been removed from a proboscis. This novel method would eliminate a need for the analyzer to extend or skip a timing cycle, and may also eliminate a need for additional sample volume.
One possible way to conduct the spectrophotometric measurement after the metering tip is removed from the proboscis is to first seal or crimp the end of the metering tip, spontaneously forming a cuvette for holding the remaining portion of the sample during the measurement.
An improved analyzer process according to the principles of the present invention may include the steps of sample handling, aspirating a portion of the sample into a metering tip, and dispensing a portion of the sample onto a test element or slide. Next, a proboscis holding the metering tip may move to a tip ejection position. Then, a position sensor may be used to detect that the proboscis and metering tip have moved to the tip ejection position, and the sensor may trigger a clamp to hold the tip in position while the proboscis lifts away. Preferably after a short delay to let the sample fluid settle, a spectrophotometer reading is taken through the cone of the tip. The clamp may then be released, allowing the tip to fall into a disposal container.
In optional steps, a metering pump may pull sample fluid a short distance up into the tip to form a small bubble of air at the tip's end, and the end of the metering tip may be sealed to form a virtual cuvette.
Another optional step of the present invention may involve aspirating a selected auxiliary volume of sample liquid from the tip or cuvette after the sample quality measurement, and passing this auxiliary sample to a wet chemistry analyzer system. Or, rather than a wet chemistry system, the auxiliary sample may be passed to a diluter system, where it is diluted and passed on to the sample processing apparatus for repeating at least one clinical chemistry test and analysis on the diluted liquid.
Accordingly, some advantages of the present system and method include improved throughput, the capability to use much smaller sample liquid volumes, eliminating any need for a separate supply of cuvettes in addition to the metering tips. An additional advantage lies in providing for detection through a cone of the metering tip, rather than through any label that may be on a primary patient collection container.
Additional advantages of the present invention include conducting spectrophotometric analysis in a simpler and less expensive manner. Another advantage lies in obtaining results of spectrophotometric analysis in less time, without extending or omitting a timing cycle.
These and various other objects, advantages and features of the invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings.